Non-volatile memory devices are used in applications that require stored information to be retained even when the memory devices are not powered. Examples of non-volatile memory devices include read-only memories, magnetic computer storage devices (e.g., hard disks), optical disc drives, erasable programmable read-only memories, and flash memories.
Flash memories are used in a wide variety of electronic applications. Flash memories are able to store one or more bits of data in the form of electric charges. However, although existing manufacturing processes for forming flash memories have been generally adequate for their intended purposes, as the reliability requirement for flash memories increases, they have not been entirely satisfactory in all respects.